diff --git a/src/App.jsx b/src/App.jsx
index 7e35cc8..2a6b4ab 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -72,11 +72,37 @@ class MyComponent3 extends React.Component {
         }
     }
 }
+
+class Timer extends React.Component {
+    constructor(props) {
+        super(props);
+        this.state = { seconds: 0 }
+    }
+    
+    componentDidMount() {
+        console.log('Timer mounted');
+        this.interval = setInterval(()=>{
+            this.setState(prevState => ({seconds: prevState.seconds + 1}))
+        },1000);
+    }
+    
+    componentWillUnmount() {
+        console.log('Timer unmount');
+        clearInterval(this.interval);
+    }
+    render() {
+        return <h2>Прошло секунд: {this.state.seconds}</h2>
+    }
+}
+
 function App() {
+    const [show,setShow] = React.useState(true);
+    
 	return (
 		<>
-			<h1>Hello, React!</h1>
-            <MyComponent />
+			<h1>Таймер с классом</h1>
+            <button onClick={()=>setShow(prev => !prev)}>{show ? 'Скрыть' : 'Показать'} таймер</button>
+            {show && <Timer />}
 		</>
 	)
 }
diff --git a/src/main.jsx b/src/main.jsx
index 950e96a..7e925e8 100644
--- a/src/main.jsx
+++ b/src/main.jsx
@@ -4,7 +4,5 @@ import { createRoot } from 'react-dom/client'
 import App from './App.jsx'
 
 createRoot(document.getElementById('root')).render(
-	<StrictMode>
 		<App />
-	</StrictMode>
 )